[WIP] Cleaned up the admin, also made locale support disabled by default

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | yes (locale off by default)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

requires https://github.com/symfony-cmf/RoutingBundle/pull/157